A Note on Frame Dragging

TL;DR

This paper clarifies the terminology of frame-dragging in general relativity, emphasizing the importance of spin-orbit and spin-spin effects, and highlights the de Sitter precession as a key benchmark for experiments like Gravity Probe B.

Contribution

It clarifies the conceptual understanding of frame-dragging and related effects, proposing a more precise terminology and interpretation for experimental measurements.

Findings

De Sitter precession is a form of frame-dragging.

High-accuracy measurements of spin effects are crucial for testing general relativity.

The paper advocates for a clearer distinction between different spin-related effects.

Abstract

The measurement of spin effects in general relativity has recently taken centre stage with the successfully launched Gravity Probe B experiment coming toward an end, coupled with recently reported measurements using laser ranging. Many accounts of these experiments have been in terms of frame-dragging. We point out that this terminology has given rise to much confusion and that a better description is in terms of spin-orbit and spin-spin effects. In particular, we point out that the de Sitter precession (which has been mesured to a high accuracy) is also a frame-dragging effect and provides an accurate benchmark measurement of spin-orbit effects which GPB needs to emulate.